1. Field of the Invention
The present invention relates to a portable electronic apparatus, known as an IC card, having a keyboard and a display unit on its surface and incorporating an erasable nonvolatile memory and a control element such as a CPU.
2. Description of the Related Art
Recently, an advanced portable data storage medium in the form of a multifunctional IC card having a keyboard and a display unit formed on its surface and incorporating an erasable nonvolatile memory such as an EEPROM and a control element such as a CPU, has been developed. Such an IC card can be used as a portable calculator, as a timepiece for displaying the time, or as a so-called electronic pocket notebook in which a variety of information can be written by using the keyboard board or the display unit formed on the card surface. European Patent Disclosure No. 0167044 (published Aug. 1, 1986) discloses an IC card having a keyboard and a display unit. Alternatively, such an IC card can be inserted in an external apparatus, such as a terminal station, to exchange data therewith, and information input from such an apparatus and written in then nonvolatile memory can be changed to other information, in accordance with a command keyed-in on the keyboard.
If, however, the information input from the external apparatus and written in the memory is, for example, a trade record linked to a center system, this data change function in accordance with a keyboard command may lead to a serious problem of alteration of the record.
More specifically, specific information such as a trade record may be erroneously or intentionally changed.